Field of the Invention
The present invention relates to a displaying apparatus unit and a projection type displaying apparatus, and is suitable for a liquid crystal projector using a reflection type liquid crystal panel.
Description of the Related Art
In the conventional reflection type liquid crystal panels, a dustproof structure is necessary for a displaying element peripheral portion. This is so because there is a problem that dust on a liquid crystal cover glass is displayed in a projected image. In U.S. Patent Application Publication No. 2003/0231287, dustproof structures are formed before and after a liquid crystal panel, so dust is inconspicuous even when it is projected onto a screen. That is, a dustproof structure is formed by arranging a light polarization plate in a position spaced apart from the liquid crystal panel to surround the space between the liquid crystal panel and the light polarization plate by a frame body.
As a displaying pixel of the liquid crystal panel is downsized and the panel size is decreased, the entrance of finer dust particles sometimes poses a problem. If dust particles having the same size adhere to a liquid crystal panel cover glass surface, wavelength plate surface, and prism surface, defocus amounts projected on a projection screen become different in accordance with the positions, so the influences on the projection screen are also different.
The size of a dust particle which poses a problem when adhering to a liquid crystal panel is about the size of a pixel. On the other hand, when a dust particle adheres to the surface of a wavelength plate arranged apart from the liquid crystal panel, the dust particle is defocused on a projection screen, so the size of a dust particle allowed to adhere to the wavelength plate is larger than that of a dust particle allowed to adhere to the liquid crystal panel cover glass surface. Accordingly, the size of a dust particle allowed to adhere to an optical component in a liquid crystal panel peripheral portion is proportional to the distance from the liquid crystal panel.
A liquid crystal panel generally shifts (deviates), falls, and rotates in the X and Y directions in order to adjust the position. Therefore, a dustproof cover member in contact with the liquid crystal panel has to absorb a stress generated by displacement caused by this posture difference. Conventionally, a relatively soft (low-hardness) dustproof structure is necessary to eliminate the influence of this stress on the liquid crystal panel. Also, a quarter wavelength plate is rotated relative to the liquid crystal panel around the optical axis in order to adjust the contrast, so a stress generated during the rotation has to be absorbed. That is, in the conventional arrangement, priority is given to accuracy by absorbing the posture difference as described above, so a soft material has to be used as the dustproof cover member.